1. Field of the Invention
Aspects of the present invention relate to polybenzoxazines, an electrolyte membrane including the same, and a fuel cell including the electrolyte membrane, and more particularly, to novel polybenzoxazines, an electrolyte membrane including the polybenzoxazines for fuel cells used at high temperatures without humidity, and a fuel cell including the electrolyte membrane.
2. Description of the Related Art
Conventionally, ion conductors in which ions are transferred by applying voltage thereto have been widely used as electrochemical devices such as batteries and electrochemical sensors.
For example, proton conductors having stable proton conductivity during long-term operation at an operation temperature in the range of 100 to 300° C. with no humidity or humidity levels less than 50% are required in fuel cells so as to improve electric power generation efficiency, system efficiency, and long-term durability of elements therein. In a conventional solid polymer fuel cell having an electrolyte membrane formed of perfluorosulfonic acid, sufficient electric power generation cannot be obtained at an operation temperature of 100 to 300° C. with a relative humidity of 50% or less.
Further, fuel cells having electrolyte membranes in which a proton conducting agent is included, fuel cells having a silica dispersion membrane, fuel cells having an inorganic-organic complex membrane, fuel cells having a phosphoric acid doped polymer electrolyte membrane, and fuel cells having an ionic liquid complex membrane have been used. In addition, a solid polymer electrolyte membrane formed of polybenzimidazole (PBI) doped with a strong acid such as phosphoric acid, has been introduced in Savinell et al. (U.S. Pat. No. 5,525,436).
Such an electrolyte membrane may have an increased ion conductivity due to the phosphoric acid doping; however, mechanical properties of the electrolyte membrane may degrade. Particularly, mechanical and chemical stability of PBI doped with a strong acid, such as phosphoric acid, may degrade at a high temperature, and the phosphoric acid-trapping capability may degrade.